The oxidation mechanism investigation of benzene catalyzed by palladium nanoparticle: A ReaxFF molecular dynamics

The precious metal palladium has exhibited well catalytic effect on soot oxidation. In order to study the catalytic mechanism of palladium on soot oxidation, the oxidation process of benzene (C₆H₆), an important soot precursor, on the surface of palladium (Pd) particles is studied by reactive force field molecular dynamics (ReaxFF MD). The possible reaction pathways of C₆H₆ oxidation and state conversion of metal Pd during the oxidation process are discussed. The results show that C₆H₆ is mainly oxidized through dehydrogenation, until the hydrogen number is less than 3, then the oxygenation reaction gradually dominates. The intermediate species, most of which is C₆HO. For the important step of C₆H₆ oxidation, the ring-open is more likely to occur at the oxygen-containing site (accounted for 88%), and C2 species are mainly final products under current simulation conditions. The oxygen migration is then investigated, and the results show that the dissociated oxygen will entrance the Pd-lattice with the gaseous oxygen consumed, and finally return to the outer-surface. It is interesting to note that the oxygen in hydrocarbon oxidation products mainly (over 57%) comes from the Pd-inner lattice even during the period of the dissociated oxygen atoms keeping balance. This may be helpful to understand the coexistence of Pd and PdO during the oxidation process that found in the experiments.